Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with6.6×1020protons on target

Abstract

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: normal hierarchy∶ sin 2 θ 23 ¼ 0.514 þ0.055 −0.056 and Δm 2 32 ¼ ð2.51 AE 0.10Þ × 10 −3 eV 2 =c 4 and inverted hierarchy∶ sin 2 θ 23 ¼ 0.511 AE 0.055 and Δm 2 13 ¼ ð2.48 AE 0.10Þ × 10 −3 eV 2 =c 4 . The analysis accounts for multinucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters, jΔm 2 j, sin 2 θ 23 , sin 2 θ 13 , δ CP , and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region δ CP ¼ ½0.15; 0.83 π for normal hierarchy and δ CP ¼ ½−0.08; 1.09 π for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes factor of 2.2. The most probable values and 68% one-dimensional credible intervals for the other oscillation parameters, when reactor data are included, are sin 2 θ 23 ¼ 0.528 þ0.055 −0.038 and jΔm 2 32 j ¼ ð2.51 AE 0.11Þ × 10 −3 eV 2 =c 4 .

The NOvA Experiment

“…These effects are proportional to the number of electrons in the path of the beam, and NOvA has the longest baseline of any accelerator neutrino experiment, giving sensitivity to part of the range of possible parameters. Furthermore, the fact that the baseline and energy differs from that of the T2K experiment in Japan [3] means that comparing the results of the two experiments will result in more sensitivity than either experiment alone. To do this, the plan is to run for three years each with a neutrino then an anti-neutrino beam and compare the differences.…”

Systematics for T2K/Hyper-K (Review Talk)

“…The current T2K near detectors are able to constrain the wrong sign background component and the intrinsic ν e of the beam down to 7% and 5% respectively. We expect a slightly better Hyper-K wrong sign background constraint due to the fact that increased focusing power of the horns (from 250 kA to 320 kA) will reduce the uncertainty however the constraint from T2K is dependant on the magnetisation of the T2K near detector [5]. The intrinsic ν e component is currently constrained by making use of the ν µ -ν e correlations predicted from simulations, the uncertainties of which are expected to decrease in the future with the inclusion of replica target data for tuning the hadron production simulations [1].…”

“…A more complete explanation can be found in reference [4]. The sensitivity was calculated based on results from the T2K experiment in 2013 [5] and improvements expected for Hyper-K.…”

Neutrino detectors for oscillation experiments

“…The T2K Collaboration has successfully applied a method of fitting the near detector data with parametrized models of the neutrino flux and interaction cross sections and reduced the systematic uncertainties on the predicted rate of ν µ and ν e at SK to a 6-7% level [2]. However, there are several limitations to this approach.…”